1. Field of the Invention
This invention relates to the field of chain, and more specifically to a method of manufacturing hollow link chains and particularly rope chains, having flattened and highly reflective facets formed on exterior surfaces of its links, and the chains formed by the method.
2. Description of the Prior Art
Jewelry rope chain, such as used for necklaces and brackets and the like are made from a helicoid configuration of a large number of individual links, which are interconnected to form a double helix helicoid resembling a rope, and thus are given the term "rope chain." Due to high cost of the precious materials, e.g. gold, platinum, silver, etc. used to form rope chains, manufacturers have made many innovations to reduce the amount of precious material needed to form a rope chain of a given diameter and length. These methods include using hollow wires to form the links assembled into the rope chain, using wires which have unique cross sections to form the individual links, such as taught in U.S. Pat. No. 5,185,995 to Dal Monte, using particular ratios of number of links per turn of the helicoid, such as taught in U.S. Pat. No. 4,651,517 to Benhamou et al.; using overall link shapes, as disclosed in U.S. Pat. No. 4,996,835 to Rozenwasser as well as other innovations and techniques. Balanced against the weight saving concern, is the necessity that the aesthetics of the finished product must not be unduly compromised, and hopefully enhanced, and the often higher laser and/or equipment costs required.
In the last several years so-called "diamond cut" rope chains have been popular. The "diamond-cuts" give the chain numerous facets, which reflect light much as do facets on precious stones, giving the rope chains enhanced sparkle. In the case of rope chains made from solid links, most often the facets are formed by grinding or shearing off some of the material from areas of the links in the assembled rope chain to form the facets.
In cases where hollow links are used, the links in the areas where precious material will be sheared or grinded must be thick enough so that the links will not be excessively thinned or sheared through. U.S. Pat. No. 5,412,935 to Rozenwasser utilizes special hollow links with a ring region of enhanced thickness around its outer perimeter. Portions of this ring region are sheared off when the rope chain is carried on a drum, or is said to be ground off to form the diamond cut facets on the finished rope chain. While the method of Rozenwasser does allow for diamond cutting of the hollow links, the resulting diamond cut rope chain has a different appearance than that of normal diamond cut rope chain. Moreover, the inventor believes the Rozenwasser rope chain would be difficult to manufacture since it requires first forming precious metal plate having an unusual profile with an area of enhanced thickness, and then carefully wrapping this plate around a base metal anvil such that the area of enhanced thickness is positioned on an outer perimeter thereof. These wires are then formed into links which are assembled into rope chains.
In lieu of grinding or shearing hollow links to form hollow facetted rope chains, a methodology has been developed to inwardly deform regions of the hollow rope chain's links to form generally flattened regions, which flattened region art as facets. U.S. Pat. Nos. 5,437,149, 5,353,584, 5,129,220 and 5,125,225 to Strobel et al. disclose this methodology and chains formed by the method. In the Strobel et al. methodology and chain, unfacetted hollow rope chain is wound around a freezing cold drum, and water is applied to freeze the rope chain onto the drum to immobilize the rope chain thereon. A burnishing/hammering tool is then applied longitudinally along an outer line along the drum. As the burnishing to tool is slowly moved longitudinally along the drum, regions of links of the rope chain are deformed inwardly, forming facets thereon. The direction of travel of the burnishing tool is in a direction generally perpendicular (transverse) to the length of the chain, thereby effectively preventing any stretching of the rope chain as it is being burnished or hammered. The rope chain is then removed from the drum, rotated by a certain number of degrees (e.g. by 90 degrees to form a rope chain with facets on four sides, and by 45 degrees to form a rope chain with facets on eight sides) and is rewound on the drum for further facetting. The Strobel et al. process functions well in allowing hollow rope chain to be facetted. However, a considerable amount of skilled labor is involved in carefully positioning and repositioning the rope chain around the drum between the cycles of forming the facets on different sides of the rope chain. The process of drum turning must be closely supervised, requiring that skilled personnel be present during the entire process. While the Strobel et al. process is particularly useful in facetting rope chains, it can also be utilized to form facets on other types of hollow link chains.
In order to understand the methodology of Strobel et al. and of the invention herein, it is helpful to understand how rope chains, both solid of hollow linked, are manufactured. Rope chains, whether formed from hollow or solid link wire, are manufactured using a plurality of individual links with a gap between their two ends. These links gaps are interconnected with or "woven" together with adjacent links gaps offset from each other by 180 degrees. During the assembly of the individual links into the rope chain, a pair of binding wires are twisted around the rope chain in its two helical furrows to hold the links in place. As additional links are added to the growing chain, the binding wires continue to be twisted around the length of rope chain being formed. After a desired length of link wire is formed, most adjacent links in the chain are soldered together. The soldering of some of, but not all of the links to both adjacent links prevents the rope chain from falling apart, yet gives the chain overall flexibility. The binding wires can be steel, copper, or other materials. After the soldering step is completed, the binding wires are removed from the now assembled rope chain. In the case of hollow rope chain, the individual links are made from link wire which has a precious metal plate wrapped around a core of a base metal such as copper, aluminum, iron, etc. If the precious metal plate wraps completely around the base metal core, the link wire is called "seamless". If the precious metal plate does not completely encircle the base metal core, leaving a gap, the link wire is termed "seamed" link wire. The link wire is then formed into individual links by coiling the link wire around a form to establish the desired link shape, e.g. a circle, an oval, a hexagon, etc., and then slicing the coil perpendicular to the coil to form the individual links. After the soldering step and the binding wires are removed, the base metal core in the links of the assembled rope chain is dissolved out by chemical treatment. Acids are typically utilized to dissolve out copper and iron cores and caustic soda functions well to dissolve out aluminum cores. The completed hollow rope chain can then be further manufactured into facetted rope chain by the method of Strobel et al.
As stated above, in the method of Strobel et al., a burnishing tool is applied generally perpendicularly to the length of the rope chain while the completed rope chain is rigidly retained on the drum, to form a series of flattened facets on one side of the chain. Since the rope chain is rigidly frozen to the drum, the rope chain does not move during this process, and the delicate hollow rope chain is prevented from stretching longitudinally and being distorted, which is a problem with hollow rope chain.
Diamond milling machines, such as that model 2300/2T diamond milling machine manufactured by F.O.V., S.A.S, of Vicenza, Italy have been used for forming facets on solid rope chain. In the use of diamond milling machines, solid rope chain which has been completely manufactured, is arranged to travel longitudinally along a path, where it passes over pulleys, exposing one side of the rope chain for diamond cutting, with the other side remaining in contact with the first pulley. Spinning adjacent to a first pulley is a first disk carrying cutting bits which impinge upon the exposed first side of the rope chain, and shear off portions of the link material on the first side of the rope chain, leaving a first series of facets. The cutting bits are often diamond tipped, or made of carbide. The half facetted rope chain then passes onto a second pulley, where the now facetted first side is in contact with the second pulley, and the second, uncut side is exposed. Spinning adjacent to the second pulley is a second disk carrying cutting bits which impinge upon a second side of the rope chain, and shear off portions of the link material on the second side of the rope chain, leaving a second series of facets. The process allows forming all the facets on the rope chain in a single longitudinal pass of the rope chain through the diamond milling machine. The diamond milling machine process for forming solid diamond-cut rope chain using solid rope chain as a starting material is efficient since the diamond milling machines, in general, are fully automated and require little direct supervision by skilled workers.
U.S. Pat. No. 5,471,830 to Gonzales discloses the use of diamond milling machines to form a mirrored finish on a chain with a circular perimeter. Gonzales states that as a final method to form the mirrored finish, cutting tools are oriented such that material will be cut from the outer surface of the chain. However, contrary to the statements in Gonzales, it has been the instant inventor's experience that any attempt to process hollow link chains on diamond milling machines results in the chain being twisted, distorted, and torn apart.
Indeed, while these diamond milling machines, (which employ a dry process in contrast to the Strobel immobilization by freezing process) have proven useful in facetting solid chains of several types, including rope chains, they have not been found useable in forming facetted hollow chains. First, there has previously been no known way of forming the facets on areas of the chain without unduly cutting into the walls of the hollow chain links. Furthermore, since the cutting is in a longitudinal direction, considerable longitudinal stress is put on chains during the facetting process, which in solid chains is fairly well tolerated without unduly stretching of the chain, but which excessively stretches and distorts hollow link chain. Manufacturers would welcome a method to utilize longitudinal diamond milling machines and the like to manufacture facetted hollow link chains, including facetted hollow link rope chain.